FEM Modeling and Capillary Wave Analysis of Electrowetting Induced Droplet Oscillations

Abstract

In this work we investigate Electrowetting-on-Dielectrics (EWOD) induced droplet oscillations, occurring in water droplets with relatively large volumes. Said oscillations will trigger capillary waves on the surface of the actuated liquid. We provide finite element simulations as well as an analysis of the acting inertial and surface tension forces. It was found that droplet height and droplet contact angle (CA) tend to move in an oscillatory motion and are therefore affected by superposed oscillation frequencies, if the volume of the oscillating droplet is big enough and the Weber number is sufficiently high. We present limiting values for the droplet size, for a material property measurement method proposed earlier, which is based on frequency and oscillation decay behavior.